feat: backend executor implement

internal/transaction/coordinator.go

@@ -93,7 +93,28 @@ func (c *Coordinator) ExecuteStep(ctx context.Context, transactionID string, int
 		return step, nil
 	}
 	if step.Status == StepFailed {
-		return step, fmt.Errorf("external step already failed: %s", step.Error)
+		inspection, inspectErr := operation.Inspect(ctx)
+		if inspectErr != nil {
+			return step, c.uncertain(ctx, transactionID, intent.Key, fmt.Errorf("inspect failed step: %w", inspectErr))
+		}
+		switch inspection.Status {
+		case InspectionApplied:
+			if _, err := c.store.ReopenFailedStep(ctx, transactionID, intent.Key, "manual resume found failed step applied"); err != nil {
+				return step, err
+			}
+			return c.completeApplied(ctx, transactionID, intent.Key, inspection)
+		case InspectionNotApplied:
+			reopened, err := c.store.ReopenFailedStep(ctx, transactionID, intent.Key, "manual resume found failed step not applied")
+			if err != nil {
+				return step, err
+			}
+			step = reopened
+			created = true
+		case InspectionUnknown:
+			return step, c.uncertain(ctx, transactionID, intent.Key, errors.New("inspect failed step returned UNKNOWN"))
+		default:
+			return step, c.uncertain(ctx, transactionID, intent.Key, fmt.Errorf("inspect failed step returned invalid status %q", inspection.Status))
+		}
 	}
 
 	if !created {